Thursday, 13 February 2014

Cello Repair 11/2013

This cello belongs to a friend who
played it in his school's Chinese Orchestra when he was younger. It
had survived what I believe was a relatively major fall that saw the
fingerboard take the brunt of the impact.

Fortunately, most of the force of the
fall was used to break the glue holding the fingerboard to the neck, resulting in the fingerboard breaking off and taking a small chunk of
the neck it it. For those who don't know, violins are held together
by hide/animal glue, which is designed to give way in some situations
before the wood cracks.

Other than having a small chunk of its neck torn off, the
instrument suffered no other forms of structural damage Gluing the
fingerboard back on is (and was) a messy and frustrating business as it tends
to slip and slide, smearing glue all over the place (in any case,
dried hide glue is easily washed off with hot water).

One other complaint my friend gave me
was that he did not like the sound of his instrument (before the
fall)! Besides new strings (which the instrument was in dire need of), I noticed that his bridge
was also thicker than normal. Violin shops sometimes leave the
bridge (and the entire violin for that matter) a bit thicker than
recommended on student instruments to negate the lower quality of the
wood used as well as to allow the instrument to better survive repeated abuse.

However, a thick bridge muffles the
sound of an instrument as it cannot efficiently transfer string
vibrations to the body of the instrument. On the flip side of the
coin, an overly thin bridge also does detriment to the tone of the
instrument and will also warp with time (due to pressure from the
strings).

Thinning the bridge (I used a belt
sander) tested my patience as bridge thickness is measured to an
accuracy of 0.1mm (using digital calipers) and it is very easy to over-thin the bridge. Overall, I had to thin
the thickest parts of the bridge by around 1.2mm and the thinner
parts by as little as 0.3mm. The results were quite satisfactory as
constant checking ensured that I did not shave off too much (a lesson learnt from carving a violin bridge for the first time).

Putting everything back together, the
cello spoke again after many years in storage. A final verdict on the
tone (normal student grade tone, rounded, slightly bright, a little
thin) however, will have to wait for new strings!